Jom build/install issue with OpenSSL and ExternalProject_Add

I have discovered an issue when using Jom to build OpenSSL using ExternalProject_Add with CMake.

After OpenSSL finishes building, when Jom is invoked to perform the install step, there still seems to be handles open to other files (specifically what seems to be temporary makefiles)

E.g. Trying to rename makefile-25040 -> makefile: Permission denied

This can be reproduced with the CMakeLists.txt file below:

cmake_minimum_required(VERSION 3.22)

project(jom-repro)

include(ExternalProject)
include(ProcessorCount)

ProcessorCount(CPU_COUNT)

ExternalProject_Add(
  openssl
  GIT_REPOSITORY https://github.com/openssl/openssl.git
  GIT_TAG openssl-3.2.0-alpha2
  GIT_SHALLOW ON
  UPDATE_COMMAND ""
  BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR}/openssl/build
  CONFIGURE_COMMAND perl <SOURCE_DIR>/Configure no-docs no-tests no-legacy /FS
                    --prefix=${CMAKE_CURRENT_BINARY_DIR} --openssldir=ssl
  BUILD_COMMAND jom -j ${CPU_COUNT}
  INSTALL_DIR ${CMAKE_CURRENT_BINARY_DIR}
  INSTALL_COMMAND jom install_sw)

With this CMakeLists.txt file in a new directory, simply run:

cmake -B build

cmake --build build

And see the error occur:

[3/4] Performing install step for 'openssl'
FAILED: openssl-prefix/src/openssl-stamp/openssl-install C:/.../jom-repro/build/openssl-prefix/src/openssl-stamp/openssl-install
cmd.exe /C "cd /D C:\...\jom-repro\build\openssl\build && jom install_sw && "C:\Program Files\CMake\bin\cmake.exe" -E touch C:/.../jom-repro/build/openssl-prefix/src/openssl-stamp/openssl-install"

jom 1.1.4 - empower your cores

        C:\...\jom_1_1_4\jom.exe / depend
        C:\...\jom_1_1_4\jom.exe / depend
Trying to rename makefile-25040 -> makefile: Permission denied
jom: C:\...\jom-repro\build\openssl\build\Makefile [depend] Error 13
        C:\...\jom_1_1_4\jom.exe / depend
        C:\...\jom_1_1_4\jom.exe / _build_libs
        C:\...\jom_1_1_4\jom.exe / _build_modules
jom: C:\...\jom-repro\build\openssl\build\Makefile [build_programs] Error 2
ninja: build stopped: subcommand failed.

The reason I am reporting this here and not to OpenSSL is this above works as expected if using nmake, it just takes a lot longer. If I run the build command a second time, it succeeds.

Update: One workaround for this is simply to use nmake in the install command, but it feels like jom should work and that this bug is maybe a symptom of something more serious potentially? It isn't a huge deal but I just wanted to mention it in case. Thanks!